Culture

In St. Louis, corms must be lifted in fall each year. Although corms may be left in the ground year-round in USDA Zones 7-10, it is generally believed that plants in these areas will flower best if corms are dug annually there as well. Best grown in humusy, medium moisture, well-drained soils in full sun. Adapts to a wide range of soils except heavy clay. Site plants in locations protected from strong winds. Corms may be started indoors in early spring (for earlier bloom) or planted directly in the ground after last frost date. Corm size determines planting depth and spacing. Plant corms 2-6” deep (2-3” for small corms and 5-6” large ones) and 4-6” apart. Provide consistent moisture during the growing season, especially during dry summer periods, and do not allow soils to dry out. After bloom, reduce watering. After foliage yellows and before the first significant fall frost, dig up corms, cut off stems and leaves, separate cormels (small corms at the base), dry corms and cormels, discard any diseased or damaged corms and store remaining ones for winter in a dry medium in a cool, frost-free location. If fungal diseases have been a problem, consider dusting corms with a fungicide immediately prior to storage. Corms may also be planted in containers with corms stored for winter in the same manner as if they were planted in the ground.

Noteworthy Characteristics

Gladiolus produce sword-shaped medium green leaves (to 2’ long) in upright fans. Funnel-shaped flowers on slender scapes blooming bottom to top in summer to early fall. Extensive range of flower colors, including shades of white, cream, yellow, orange, red, pink, lavender, purple and green. Most of the gladiolus sold today are hybrids which are commonly designated as Gladiolus x hortulanus. Three main hybrid groups exist:

a. Grandiflora hybrids. Funnel-shaped, large-flowered gladiolas with blooms 4-6” wide on scapes 3-6’ tall. Up to 30 flowers per spike. Extensive range of flower color. Most difficult group to grow well in gardens.
b. Nanus hybrids. Miniature hybrids with small flaring blooms to 3” wide on scapes to 1.5’ tall.
c. Primulinus hybrids. Hooded-type flowers on scapes 2-4’ tall. Flowers generally more graceful and looser on stems. Butterfly hybrids, often included as a subgroup herein, feature flowers with ruffled petals and contrasting throat blotches and other markings on scapes 2-3’ tall.

Genus name comes from the Latin word for a small sword in allusion to the shape of the leaves. The plants are also sometimes called sword-lilies but people generally use the Latin plural gladioli.

Problems

Susceptible to Bortytis, crown rot, rust, wilt and mosaic virus. Watch for aphids, mealy bugs, spider mites and thrips. If thrips were a problem during the growing season, consider treating corms with an insecticide prior to storage.